Nowadays, renewable resources are considered to be the new challenge in the development of Sustainable/Green chemistry. Interest in the application of biomass has increased considerably during the last decade because biomass-based resources are renewable and CO2 neutral. In addition, the projected long-term limitations on the exploitation of fossil feedstock, the recent increases in crude oil prices and environmental concerns regarding the local air pollution, the global warming problems caused by CO2, the biodegradability and biocompatibility of many petrochemical based products have also played a role in this respect. Today the world production of renewable biomass is about 200·109 t/a of which 130·106 t/a are fats and oils and only 7% of the total biomass production capacity are used for food, feed and non-food applications. These figures compared to the world capacity of extracted fossil fuels which is only 7·109 t/a show the huge potential of renewable biomass for energy, chemicals and material production. According to the Directive 2003/30/EC of the European Parliament and of the Council by 31 Dec. 2010 biofuels shall be 5.75% of the transportation fuels and according to the US roadmap for biomass technologies—2020 vision goals, biofuels will meet 10% of the fuels, and biomass-based chemicals 18% of the chemicals in the US market.
Vegetable oils and their derivatives are important feedstock for the industry with a broad spectrum of applications such as in foodstuff chemistry, pharmacy, cosmetics, plastics, detergents, biolubricants and in the energy field with the production of biodiesel mainly by transesterification reactions with methanol or ethanol to obtain fatty acid methyl (FAME) or ethyl esters (FAEE).
Catalytic hydrogenation of renewable vegetable oils and their derivatives constitutes a major unit operation in the chemical industry. In such kind of hydrogenation processes of C═C units in unsaturated fatty acids of vegetable oils are commonly used heterogeneous catalytic systems based on nickel, palladium, copper, copper-chromite, platinum etc. However, for edible oil hydrogenation heterogeneous catalysts based on nickel has been the choice of industry. Traditional Ni-based commercial heterogeneous edible oil hydrogenation catalysts produced high amounts in trans-fats (up to 40%). In recent years the negative health effects of trans-fats received increasing attention and decisions have been made in Europe to limit and in USA to declare the trans-isomers contained in fatty foodstuffs which caused a demand for hardstocks with lower trans-isomers content. Therefore, there is increasing interest in the development of new industrial hydrogenation processes producing low amounts of trans-fats. One development may involve the use of homogeneous transition metal complexes as edible oil hydrogenation catalysts. Several attempts have been made to develop homogenous systems which would allow conducting hydrogenation also to saturated compounds under milder conditions in order to improve colour quality of the products and to make the process more economic. Unfortunately, homogenous catalysts based on transition metals modified with conventional phosphites as known from the state of the art suffer from many disadvantages: for example they lack stability against water, they are difficult to remove from the hydrogenation products and/or they simply do not show a sufficient activity.
It has therefore the object of the present invention to overcome the disadvantages known from the state of the art and to provide a cost-effective process for hydrogenation of fatty acid esters which involves a homogenous catalyst system based on transition metals modified with sulfonated phosphites which is stable against hydrolysis, resistant to oxidative destruction, easy to remove from the reaction mixture and exhibiting a high activity.